I guess the rims may be rather worn so why not put some new ones on in 700c size, you could then use clinchers, tubs are expensive, a pain to repair and really don't offer much of an advantage for he road cyclist. The bike looks interesting, a quality bike in it's time, around mid seventies I would say. The suicide levers look a bit out of place but the lugwork is lovely. Worth restoring I would say. Don't know who or what ATR is though, maybe someone else on here might know, maybe it's eroneous as the paint job would have been applied later.